1. Field of the Invention
The present invention relates generally to the field of smoke generators, and more particularly to an improved smoke generator which is particularly adapted for use in association with other apparatus, to test the sealing integrity of a package.
2. Description of the Prior Art
Many forms of smoke generators are, of course, known.
U.S. Pat. No. 4,205,551 (Class 73/52), which is assigned to the assignee of the present application, discloses apparatus for testing the strength of a seal provided between an underlying substrate material and an overlying sheet material. That patent mentions the introduction of an optical dye to visibly indicate the locations of leaks and imperfect seals, but does not disclose specific apparatus by which such dye may be generated.
In recent years, flexible packaging has experienced a tremendous growth. Conventional rigid "tin cans" are being progressively replaced by "flexible cans" and pouches. Such pouches are also used in the medical fields to store surgical instruments and the like. Generally, a flexible pouch includes two overlying pieces of sheet material which are secured to one another along the peripheral margins thereof. Depending upon the pouch materials, such seals may be provided by a suitable adhesive, by heat sealing, or by other means.
The growth of flexible packaging has been accompanied by a need to test the integrity of the seals. The degree of sealing integrity is related to the item contained. Food products and sterile surgical instrument require the highest degree of sealing integrity.
In order to test the seal strength, it is common practice today to cut out a portion of the seal, and subject such specimen to a conventional tensile test. This is typically shown in a photograph appearing on page 46 of the September 1980 issue of the magazine, Paper, Film & Foil Converter (Maclean-Hunter Publishing Corp.). However, this conventional testing method has a number of serious drawbacks. For example, one never knows whether the test specimen, which has been cut from a larger package, contains an imperfection. If the imperfection were elsewhere, the specimen might pass, without discovery of the leak.
The aforesaid U.S. Pat. No. 4,205,551 discloses apparatus wherein a pouch is tested by inflation. If an optical straining dye is used, the pouch may be visually examined to pinpoint the location of leaks. Indeed, leaks through holes or channels of less than 0.2 microns can be detected. If such leaks recur in the same location, this may indicate a correctable condition.